Coriolis rate of rotation sensors are generally known from the prior art. They serve to measure an external rotational rate of a body or a system about one or two axes. The axis or the axes is/are defined relative to the body or system to be measured and described by means of a coordinate reference system, that is to say, in the case of two axes, orientated orthogonally relative to each other. The axes are also generally referred to as measurement axes. Coriolis rate of rotation sensors use the Coriolis forces which occur during rotation about a measurement axis on a moved spring/mass system.
Due to miniaturisation and low production costs, acceleration sensors (for detecting linear accelerations) produced using MEMS technology are being increasingly widely used. Whilst MEMS acceleration sensors are already produced in large quantities and are comparable in terms of performance with components produced using conventional technologies, the system construction and the corresponding process technology must be far more sophisticated in rate of rotation sensors owing to the very small force relationships. This explains why there are already known for acceleration sensors numerous MEMS designs which can not only detect inertial movements in the direction of one spatial axis but which are instead sensitive in two or three dimensions, that is to say, in the direction of all the spatial axes. For rate of rotation sensors, the implementation of 3D sensitivity in a MEMS component is complex since various drive and sense modes must be excited and read in a controlled manner. The mechanical and electrical crosstalk of the drive in the sense mode on the one hand and the crosstalk of the individual sense modes between each other is intended to be suppressed.
DE 10 2007 012 163 A1 discloses a rate of rotation sensor and a method for the production thereof. The rate of rotation sensor comprises a substrate which is orientated in the XY plane of a reference coordinate system, at least two base elements and reading devices. The base elements themselves each comprise a frame, a suspension of the frame on the substrate, at least one seismic mass, a suspension of the seismic mass on the frame and drive means for driving the base elements. The base elements are connected to each other by means of at least one coupling bar which is arranged on the substrate. Due to the arrangement of the coupling bar on the substrate, the movement possibilities thereof relative to the substrate are defined, such as, for example, degrees of freedom of its movement are reduced, so that disruptive deflections or parasitic oscillations of the seismic masses are reduced or suppressed via the connection with the coupling bar. The rate of rotation sensor disclosed is suitable for detecting rates of rotation about one or two spatial axes. A detection of rates of rotation in all three spatial directions is not possible with this rate of rotation sensor according to the prior art.
EP 1775551 A1 discloses a rate of rotation sensor which is constructed in a silicon wafer by means of MEMS technology. It has an annular region which is suspended on a central region by means of eight resilient bar elements. The annular region can carry out primary and secondary vibrations about the central suspension. The primary vibration is excited by actuation electrodes in a cos 2θ mode. When an external rate of rotation Ω acts about an axis perpendicularly relative to the annular region, there is produced a Coriolis force which in turn produces a secondary vibration in the sin 2θ mode. It is only possible to detect an external rate of rotation about one axis of rotation with this rate of rotation sensor according to the prior art.
US 2007/0266785 A1 discloses a rate of rotation sensor for detecting rotation about a detection axis (Y axis). It has a support structure and two masses which are flexibly connected to the support structure in such a manner that they can carry out movements in two opposite directions along a drive axis perpendicularly to the detection axis. A Coriolis force, which results in a deflection or detection movement about the detection axis, acts on the moved masses in accordance with the direction of rotation of the external rate of rotation to be detected. The rate of rotation sensor disclosed detects an external rate of rotation in a direction perpendicular to the drive axis. It is not possible to detect external rates of rotation with components in three spatial directions (3D sensor) with this rate of rotation sensor.
In order to be able to detect rates of rotation in all three spatial directions or rates of rotation with components in all three spatial directions, it is known from the prior art to combine a plurality of one-dimensional or two-dimensional individual sensors to form an inertial measurement unit (IMU). There are constructed rate of rotation sensors for detecting rates of rotation in one direction, that is to say, one-dimensional individual sensor elements (sensor chips), or in two directions (two-dimensional individual sensor elements) in a state combined on a chip or printed circuit board plane or in a corresponding sensor housing, which is also referred to as hybrid construction or sensor cluster. A disadvantage in inertial measurement units with hybrid construction or a combination of a plurality of different individual sensor designs at the chip level is the relatively complex production and the relatively high spatial requirement because it is necessary to provide a corresponding individual sensor structure having drive masses, detection units, drives and detection systems for detecting rates of rotation in the different spatial directions.
A method for producing such a hybrid construction is known, for example, from DE 10 2006 016260 A1. There is provided a wafer having corresponding active structures, for example, one or two-axis individual sensors which are inherently independently functional, and housed with a cap wafer which has cavities or recesses for the individual sensors. A Coriolis rate of rotation sensor which is suitable for detecting rates of rotation in three spatial directions and a method for the production thereof is disclosed in “Novel 3-Axis Gyroscope on a Single Chip using SOI Technology” by M. Traechter, T. Link, J. Dehnert, J. Auber, P. Nommensen and Y. Manoli, Inertial Sensors and Systems, HSG-IMIT, Villingen-Schwennigen, Germany. The publication describes a sensor cluster, in which a conventional out of plane sensor (sensor in which the detection axis projects out of the substrate plane) is combined with two in plane sensors (sensor in which the detection axis is in the substrate plane) in order to produce a sensor unit which is suitable for detecting rates of rotation in three spatial directions. As a result, the sensor unit described has three individual sensor elements which are inherently independently functional and which detect a rate of rotation in a specific assigned spatial direction (X, Y or Z). The term inherently functional means that each individual sensor element has all the functional units necessary for detecting the respective assigned rate of rotation, such as drive masses, detection masses, drive units or drive electrodes and detection units or detection electrodes. The correspondingly high number of functional units contains specific disadvantages, such as high production costs, great production complexity, in particular complex assembly, often problematic coordination of the individual sensor elements with respect to each other, complex housing and large dimensions. Those particular disadvantages and the implementation of a plurality of individual sensor elements which each detect an assigned rate of rotation in a specific spatial direction are intended to be avoided with the present invention.
WO 92/21000 discloses a micromechanical Coriolis rate of rotation sensor having a support structure which is rotatably suspended about a Z axis and on which in turn four seismic masses are arranged offset through 90° about the Z axis by means of flexible bars. The sensor can detect rotational oscillations about all three spatial axes. Rotations about the X and Y axis are detected by a displacement of the seismic axes themselves, rotations about the Z axis by means of a rotation thereof transmitted by the seismic masses to the support structure.